Single Carrier Block Transmission (SCBT) is a very attractive technique for wireless communications. In an SCBT arrangement, a block of symbols (e.g. QAM or PSK symbols) with length N is preceded by a guard interval, which can employ either a cyclic prefix (CP) or zero padding (ZP). A system employing SCBT is equivalent to an OFDM system with full spreading, if an N×N Fourier matrix is used as the spreading (code) matrix. Mathematically, the transmitted signal, s, from a spread OFDM system can be written as.s=PF−1Cx  (1)where x is the N×1 vector of the information symbols, C is the N×N spreading matrix, F−1 is the inverse Fourier transform matrix (also N×N). The matrix P creates the guard interval (GI) and is of the size (N+NGI)×N, where NGI is the length of the guard interval GI.
In the case where the guard interval employs a cyclic prefix (CP), then the P matrix is:
                    P        =                              [                                                            0                                                                                    N                        GI                                            ⁢                      xN                                        -                                          N                      GI                                                                      ❘                                  I                                      N                    GI                                                                              I                N                                      ]                    .                                    (        2        )            On the other hand, when the guard interval employs zero padding, then the P matrix is:
                    P        =                              [                                                            0                                                                                    N                        GI                                            ⁢                      xN                                        -                                          N                      GI                                                                      ❘                                  0                                      N                    GI                                                                              I                N                                      ]                    .                                    (        3        )            
It can be shown that SCBT is a special case of the above form, where the spreading matrix is the Fourier matrix, i.e. C=F. In that case we have:s=Px.  (4)This means that the simple transmission of the symbol vector x is preceded by a guard interval GI.
A system employing single carrier transmission with the guard interval as described above has the advantages of an OFDM system in dealing with multipath interference, but does not have some of the disadvantages of OFDM systems, namely high Peak-to-Average-Power-Ratio (PAPR) and the need for high resolution ADC. In terms of performance, a single carrier system with a guard interval outperforms OFDM systems, if a high rate channel code (or no coding) is used.
Meanwhile, new communication systems and networks are being developed to operate with increasingly higher data rates. For example, new wireless personal area networks (WPANs) are being developed in the 60 GHz band that can communicate at multigigabit/second data rates.
So, it would be desirable to employ SCBT for these wideband, high data rate WPANs.
However, to have a robust high rate wireless communication system over multipath channels, a channel code must be used. While implementation of the encoder (e.g. a convolutional encoder) is often simple, implementation of the decoder (e.g. a Viterbi algorithm) is generally much more difficult. When the transmission rates in a wireless communication system are very high (e.g., multi-gigabits/second), then the existing digital technology cannot provide the required processing speed for a straight forward implementation of the decoder. For example, with today's technology, a Viterbi decoder with multi-gigabit rates (e.g. 3-5 Gbps) cannot be implemented.
Accordingly, it would be desirable to provide a method of single carrier block transmission capable of operating at higher data rates. It would also be desirable to provide a wireless device that includes a single carrier block transmitter capable of operating at higher data rates. It would further be desirable to provide a method of receiving a single carrier block transmission capable of operating at higher data rates. It would be still further desirable to provide a wireless device that includes single carrier block receiver capable of operating at higher data rates.
In one aspect of the invention, a method of transmitting data comprises: dividing a set of data into a plurality of data streams; separately encoding each of the data streams with a corresponding error correction code to produce a plurality of encoded data streams; generating a single carrier block transmission (SCBT) signal from the plurality of encoded data streams; and transmitting the SCBT signal.
In another aspect of the invention, a wireless device comprises: a demultiplexer adapted to divide a set of data into a plurality of data streams; an error correction encoding unit adapted to separately encode each of the data streams with a corresponding error correction code to produce a plurality of encoded data streams; a transmission signal processor adapted to produce a plurality of symbols from the plurality of encoded data streams; and a single carrier block transmission (SCBT) modulator adapted to produce an SCBT signal from the plurality of symbols.
In yet another aspect of the invention, a method of receiving data comprises: processing a single carrier block transmission (SCBT) signal to produce received symbols; generating a plurality of encoded data streams from the received symbols; separately decoding each of the encoded data streams to produce a plurality of decoded data streams; and combining the decoded data streams.
In still another aspect of the invention, a wireless device comprises: an SCBT demodulator adapted to demodulate a single carrier block transmission (SCBT) signal and to generate therefrom received symbols; a receiver signal processor adapted to produce a plurality of encoded data streams from the received symbols; a plurality of error correction decoders, each adapted to decode a corresponding one of the encoded data streams, to produce a plurality of decoded data streams; and a multiplexer adapted to combine the decoded data streams.